[120.02] EUV and soft X-ray emission from clusters of galaxies

M. Bonamente, R. Lieu (UAH), J.P.D. Mittaz (MSSL)

Clusters of galaxies are found to possess a diffuse EUV
emitting component unrelated to the hot intra-cluster medium
(ICM) at X-ray temperatures. The EUV emission does not
resemble the X-ray morphology of clusters: at the cluster
core the EUV contours are organised, but at larger radii
they become anisotropic, and therefore unrelated to the hot
ICM.

Joint spectral analysis of EUVE/DS and ROSAT/PSPC data
showed clear evidence for a soft X-ray emission in excess of
that expected from the hot ICM: the 'cluster soft-excess'
(CSE) phenomenon has been clearly detected for the Virgo,
Coma, A2199 and A1795 clusters. Thermal and non-thermal
emission models are employed to explain the CSE.

Surprising conclusions, such as pressure equipartition
between cosmic rays and the hot ICM gas, are unavoidable
consequence of non-thermal models. Aging effect due to
radiative and collisional losses are taken into account in
the spectral modelling. Thermal interpretation of the
phenomenon typically implies, on the other hand, large
masses of warm gas.

Cosmological implications of the CSE are also discussed.

The author(s) of this abstract have provided an email address
for comments about the abstract:
bonamem@email.uah.edu